multi: rename due to required maxHTLC bit

We rename `ChanUpdateOptionMaxHtlc` to `ChanUpdateRequiredMaxHtlc`
as with the latest changes it is now required.

Similarly, rename `validateOptionalFields` to
`ValidateChannelUpdateFields`, export it to use it in a later commit.

lnwire/channel_update.go

@@ -13,9 +13,9 @@ import (
 type ChanUpdateMsgFlags uint8
 
 const (
-	// ChanUpdateOptionMaxHtlc is a bit that indicates whether the
-	// optional htlc_maximum_msat field is present in this ChannelUpdate.
-	ChanUpdateOptionMaxHtlc ChanUpdateMsgFlags = 1 << iota
+	// ChanUpdateRequiredMaxHtlc is a bit that indicates whether the
+	// required htlc_maximum_msat field is present in this ChannelUpdate.
+	ChanUpdateRequiredMaxHtlc ChanUpdateMsgFlags = 1 << iota
 )
 
 // String returns the bitfield flags as a string.
@@ -26,7 +26,7 @@ func (c ChanUpdateMsgFlags) String() string {
 // HasMaxHtlc returns true if the htlc_maximum_msat option bit is set in the
 // message flags.
 func (c ChanUpdateMsgFlags) HasMaxHtlc() bool {
-	return c&ChanUpdateOptionMaxHtlc != 0
+	return c&ChanUpdateRequiredMaxHtlc != 0
 }
 
 // ChanUpdateChanFlags is a bitfield that signals various options concerning a

lnwire/lnwire_test.go

@@ -772,7 +772,7 @@ func TestLightningWireProtocol(t *testing.T) {
 			// as being part of the ChannelUpdate, to pass
 			// serialization tests, as it will be ignored if the bit
 			// is not set.
-			if msgFlags&ChanUpdateOptionMaxHtlc == 0 {
+			if msgFlags&ChanUpdateRequiredMaxHtlc == 0 {
 				maxHtlc = 0
 			}
 

lnwire/message_test.go

@@ -690,7 +690,7 @@ func newMsgChannelUpdate(t testing.TB, r *rand.Rand) *lnwire.ChannelUpdate {
 	// as being part of the ChannelUpdate, to pass
 	// serialization tests, as it will be ignored if the bit
 	// is not set.
-	if msgFlags&lnwire.ChanUpdateOptionMaxHtlc == 0 {
+	if msgFlags&lnwire.ChanUpdateRequiredMaxHtlc == 0 {
 		maxHtlc = 0
 	}